[xcodegen] Add a couple more source file extensions

And handle case differences.

Author: hamishknight

utils/swift-xcodegen/Sources/SwiftXcodeGen/Path/FileExtension.swift

@@ -11,17 +11,23 @@
 //===----------------------------------------------------------------------===//
 
 public enum FileExtension: String {
+  case asm
   case c
+  case cc
+  case cl
   case cpp
   case def
   case gyb
   case h
+  case inc
   case m
   case md
   case mm
   case modulemap
   case o
+  case proto
   case rst
+  case s
   case swift
   case swiftmodule
   case td

utils/swift-xcodegen/Sources/SwiftXcodeGen/Path/PathProtocol.swift

@@ -74,8 +74,10 @@ public extension PathProtocol {
   func hasExtension(_ exts: FileExtension...) -> Bool {
     // Note that querying `.extension` involves re-parsing, so only do it
     // once here.
-    let ext = storage.extension
-    return exts.contains(where: { ext == $0.rawValue })
+    guard let ext = storage.extension else { return false }
+    return exts.contains(where: {
+      ext.compare($0.rawValue, options: .caseInsensitive) == .orderedSame
+    })
   }
 
   func starts(with other: Self) -> Bool {